Wireless electrical energy transmission has the advantages of safety, convenience and the like, so it is widely applied to the electronic charging field. Wireless electrical energy transmission can be achieved by means of electromagnetic induction or magnetic resonance. In general, the way of magnetic resonance is commonly used. A wireless electrical energy transmission device used for magnetic resonance includes an electrical energy transmitting end and an electrical energy receiving end to transmit energy by means of electromagnetic resonance.
In general, the electrical energy transmitting end includes an inverter, an impedance matching circuit, and a transmitting coil. The receiving part comprises a receiving coil, an impedance matching network, a rectification circuit, and a direct current (hereinafter “DC”) voltage conversion circuit (DC-DC converter). During the working process, the electrical energy transmitting end receives the alternating current to generate a spatial magnetic field, and the electrical energy receiving end inducts the alternating magnetic field to generate a desired voltage signal to the electronic equipment. However, during electrical energy transmission, the coupling between the electrical energy transmission coil and the electrical energy receiving coil may have a change. For example, a sudden increase in coupling or a sudden increase in the magnetic field energy of the transmitting coil, which causes the DC voltage Vrect after the rectification circuit exceeds the preset voltage. The excessive voltage will damage the DC-DC converter of the electrical energy receiving end, even the electronic equipment of the load side.